This invention relates to the production of improved aluminum alloy powder-derived products characterized by high yield strength at temperatures of 450.degree. to 500.degree. F. and therefore useful in aircraft and other important applications and to methods for producing the same to assure such high property levels.
The invention here described was made in the course of or under a contract or subcontract thereunder with the United States Air Force.
Aluminum alloys have enjoyed wide use in important applications such as aircraft where aluminum has become well known for its high strength to weight ratio. However, because of aluminum's limitations at elevated temperatures such as 400.degree. to 500.degree. F., aluminum is often considered less suitable than metals such as titanium since temperatures in that range degrade the strength of conventional aluminum alloys produced from ingot. For instance, forgings of aluminum alloy 2219 (5.8-6.8% Cu, 0.2-0.4% Mn, 0.05-0.15% V, 0.1-0.25% Zr, 0.02-0.1% Ti) in the T852 temper are considered to have impressive moderate temperature yield strength, but they fall far short of a desired yield strength level of over 30,000 psi at temperatures of about 450.degree. to 500.degree. F. Another approach to improve the elevated temperature strength of aluminum components is to utilize alloys that are fabricated from rapidly quenched aluminum base powders which rely on fine intermetallic particles for dispersion strengthening. For instance, U.S. Pat. No. 2,963,760 to Lyle and Towner discloses aluminum alloy powder products containing iron with or without manganese, nickel, cobalt, chromium, vanadium, titanium or zirconium, and that such are advantageous respecting strength at elevated temperatures, but these alloys and products also do not exceed 30,000 psi yield strength at 450.degree. F. Various other work has gone forward toward achieving high temperature strength in aluminum but the results have often been inconsistent, and where good strength is achieved such is often at the expense of good elongation, thus limiting the usefulness of such products which desirably have elongation exceeding 4%, for instance desirably 41/2% or 5% or more. For instance, an elongation of 51/2% or 6% or more combined with a yield strength of 30,000 or 35,000 psi at 450.degree. F. would be highly desirable in an aluminum powder-derived product, but achieving such has presented difficulties.
One recently promising inroad involves aluminum-iron-cerium alloys (Air Force Material Lab Contract F33615-77-C-5086) and the present improvement concerns methods for producing aluminum-iron-cerium powder aluminum products having good strength at elevated temperatures.